摘要:

SUMMARYThe vitamin B12requirement of several marine diatoms can be satisfied in B12−limited laboratory cultures by heterotrophic marine bacteria isolated from the same waters and from sediments. The bacteria can utilize diatom excretory products, or the remains of dead diatom cells, in the production of the vitamin.The growth of 12 B121− requiring diatoms (7 genera) in mixed cultures with 14 different bacteria (without added B12) was compared to the growth of those same diatoms in axenic cultures with excess added B12. Diatom growth was generally rapid in the first few days, followed by sustained, slower growth. The diatom yields in mixed cultures ranged from 0.8 to 84% of the yields in axenic cultures with added B12.In a detailed study of one mixed culture, increases in diatom densities were paralleled by increases in cell densities of the bacterium during the first few days of exponential diatom growth. During the period of slow diatom growth, when diatom densities oscillated but steadily increased, the decreases in diatom densities were associated with increased bacterial growth. This suggests that death of a fraction of the B12‐limited diatom population releases sufficient organic matter to stimulate growth of the bacteria and their subsequent excretion of B12; this B12in turn stimulates further growth of the diatoms.Diatom‐bacteria interactions leading to the production of B12may be important in maintaining viable populations of B12‐requiring diatoms in nutrient‐poor waters during periods between blooms, when conditions are unfavorable for r

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02709.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYBoth morphological forms ofPhaeodactylum tricornutumincorporated acetate in the light and in darkness. In the dark, the majority of the acetate was oxidized, probably by the tricarboxylic acid cycle. Although some CO2was formed from acetate in the light, most acetate carbon was found in the cellular lipids. Acetate incorporation in the light was probably a result of both direct and indirect assimilation. The organism grew poorly on acetate in the light at a very low CO2tension.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02710.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe effects of nutrients and light on sexual reproduction were investigated in 2 mating pairs ofPandorina unicoca.Strains 101–104 required nitrogen deficiency for sexual differentiation. Sulfur deficiency also appeared to be effective in evoking sexual differentiation. The time required for sexual differentiation of strains 103–104 after removal of KNO3and MgSO from the medium was 24 hr. Addition of KNO3and MgSO4after 24hr did not reverse sexual differentiation. Light was required during the first 10–12 hr. Strains 105–106 did not require a period of sexual differentiation and, exhibited mating activity in the presence of nitrogen and sulfur in the medium. Both mating pairs required light for the mating response and calcium was necessary for zygote formation. The pH range for mating activity was det

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02711.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThis paper deals with reproductive and spore germination characteristics to the systematics of the nonarticulated coralline algae. As can the articulated coralline algae, the nonarticulated coralline algae may also he divided into 2 groups on the basis of their yearly reproductive cycles, spore dimensions, and spore germination characteristics: theLithophyllum group and theLithothamniumgroup. These 2groups are basically identical with theAmphiroaandCorallinagroups of the articulated coralline algae, respectively, so far as these 3 characters are concerned. The grouping of these representatives of the Corallinaceae into 2 groups—Amphiroa—LithophyllumandCorallina–Lithothamnium—coincides with a grouping based on the manner of connection between cells of adjacent fi

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02712.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYA case of polymorphism in the desmidMicrasterias pinnatifida(Kütz.) Ralfs is described. It is based on material collected from the overflow channel of a dam in Caeté, Minas Gerais State.After careful examination of nearly 500 specimens, 26 different morphological expressions of the alga were found which led the authors to make the following deductions: (1) for delimitation of species and infraspecific taxa in desmids it is absolutely necessary to analyze sample populations; (2) the morphological characteristics presently used, for delimination of some varieties ofM. Pinnatifida (Kütz.)Ralfs seem to have no taxonomical value if only isolated individuals are examined; (3) the varietiesgranulata, inflata, andtridentatamust be considered with some caution, until further studies are carried out, because they can be merely distinct morphological expressions ofM. pinnatifida(Kütz.) Ralfs var. pinnatif

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02713.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYAcrylylcholine, choline O‐sulfate, and a yet unidentified choline ester have been isolated from cells ofAmphidinium carteri.Natural and synthetic acrylyl choline had approximately 1/4,000 the activity of acetylcholine and choline O‐sulfate about 1/20,000 the activity on isolatedMercenaria mercenariahe

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02714.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYA seasonal rhythm in blade elongation rate was observed inAlaria esculenta.Maximum (3.0–3.6 cm/week) and minimum (0.5–1.0 cm/week) rates were recorded in June and September, respectively. Translocation of growth‐promoting metabolites occurs within the main blade and between the sporophylls and blade. Bidirectional flow of growth‐promoting metabolities within the stipe was demonstrated. Seasonal effects of nutrients (NO3‐ and PO43‐) and photoperiod on blade elongation were shown in long‐term laboratory experiments. Control of seasonal blade growth by exogenous and endogenous factors

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02715.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYPhotosynthetic rates in field‐collected samples ofCladophora glomeratawere measured using the oxygen electrode technique. Rates observed were three‐ to fourfold higher than literature values obtained with the light and dark bottle method. The discrepancy appears to be due to light‐limiting conditions prevailing in the bottles. It was also found that photosynthesis inCladophoradoes not saturate at low light intensities as reported by other wo

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02716.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe facultative, heterotrophsCyclotella cryptica(sclone WT‐1‐8) andCoscinodiscussp. were selectively isolated from coastal waters by dark incubation of organically enriched solid medium.C. crypticagrows in the dark with glucose and galactose, andCoscinodiscussp. with glucose. Clone WT‐1‐8 of C.crypticagrows about twice as fast with glucose as a previously studied clone (0‐3A). In the dark with, 5 × 10−6M glucose C.crypticadivides every 3 days, while with 5 × 10−5M glucoseCoscinodiscussp. divides every 10 days. Heterotrophic growth of either diatom for 1 year does not cause a major reduction in carbon, nitrogen, chlorophyll a, and chlorophyllccontents, or in photosynthetic ability, compared to light‐grown cells. It is possible that facultative heterotrophy is of ecological benefit to these diatoms, probably for slow growth and survival during extended periods of dim

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02717.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYChloroplast morphology changes cyclically during each cell generation of synchronous photoheterotrophic cultures ofEuglena gracilisZ; these cycles persist until the transition to stationary phase. Structural modifications, development of pyrenoids, and increase in chloroplast volume accompany the cessation of cell division. Chloroplasts of stationary phase heterotrophic cells resemble those of exponential phase autotrophic cells, suggesting a relationship between chloroplast morphology and available carbon.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02718.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY